1. Field of the Invention
The present invention relates to control of peripheral equipment of a robot, and more particularly to control of a tool mounted on a distal end of a robot wrist, which has variables to be controlled in synchronism with a motion of the robot.
2. Description of Related Art
Peripheral equipment of a robot is generally controlled so that an on/off signal is output from a robot controller and a synchronization is made in a degree such that the operation of the peripheral equipment is started and stopped based on the on/off signal.
For example, in the case of a sealing robot which applies sealing material to an object in operation of the robot by means of a sealing gun mounted on a distal end of a robot wrist, a flow control of the sealing material is generally carried out so that a sealing-on signal is output from a robot controller to start the operation of the sealing gun when a nozzle tip of the sealing gun is positioned at a start point of a portion to be sealed, and a sealing-off signal is output from the robot controller to stop the operation of the sealing gun when the nozzle tip of the sealing gun reaches an end point of the sealing portion.
However, if a flow rate of sealing material discharged from the sealing gun is constant, quantity of the sealing material applied on the object changes depending on velocity of a tool center point (TCP) of the robot, i.e., velocity of the sealing gun. In this view, there has been developed and disclosed a method of making quantity of the applied material constant by changing the flow rate of the sealing material in accordance with the commanded velocity of the robot in Japanese Patent No. 2700971.
As described, the relationship between the robot and the peripheral equipment thereof is generally such that the peripheral equipment is on/off controlled based on an on/off signal output from the robot controller. Therefore, in the case where process control of variables such as flow rate and pressure is required for a tool such as a sealing gun mounted on the distal end of the robot wrist, high operational quality is hardly obtained merely by the on/off control. Also, in the above-described method disclosed in Japanese Patent No. 2700971, only the flow rate of the sealing material is changed in accordance with the commanded velocity of the robot, and the flow rate is not subjected to feedback control. This leads to a problem in that the flow rate sometimes does not agree with the target flow rate due to an operational environment such as an ambient temperature, and therefore various compensations have to be made.
An object of the present invention is to provide a robot controller capable of controlling process controlled variables of an operational tool mounted on a robot.
According to one aspect of the invention, the robot controller comprises motion control means for moving an operational tool mounted on a robot with respect to an object; supply means for supplying energy to be applied to the object through the operational tool; supply control means for issuing a supply command to the supply means, the supply command being determined based on motion variable of the operational tool in motion obtained by the motion control means; and means for feeding back a parameter representing power of the energy supplied through the operational tool to alter the supply command based on the fed back parameter.
The motion variable may be a velocity of a control point of the robot relative to the object. The supply means may be a power source for supplying a welding current, a laser oscillator for supplying a laser beam, or an electric motor for driving a pump for supplying sealing material or paint.
In the case where the supply means is the welding power source, the fed back parameter may be a welding current, and in the case where the supply means is the laser oscillator, the fed back parameter may be an excitation current of the laser oscillator.
Further, the supply means may supply energy to an operational substance to be fused so as to apply the fused operational substance to the object through the operational tool. In this case, a parameter representing power of the energy supplied to the operational substance is fed back. The operational substance may be a filler metal, and the fed back parameter may be a welding current.
According to another aspect of the invention, supply means supplies an operational substance to be applied to an object through an operational tool, a parameter representing the supply rate of the operational substance supplied through the operational tool is fed back, and a supply command is altered based on the fed back parameter. In this case, the supply means may be an electric motor for driving a pump for supplying sealing material or paint, and the fed back parameter may be a pressure of the sealing material or paint at an outlet of the operational tool.